Re: [PATCH 09/12] xfs_repair: rebuild reverse mapping btrees with bulk loader

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Thu, Jun 18, 2020 at 11:37:40AM -0400, Brian Foster wrote:
> On Thu, Jun 18, 2020 at 08:31:00AM -0700, Darrick J. Wong wrote:
> > On Thu, Jun 18, 2020 at 11:25:11AM -0400, Brian Foster wrote:
> > > On Mon, Jun 01, 2020 at 09:27:51PM -0700, Darrick J. Wong wrote:
> > > > From: Darrick J. Wong <darrick.wong@oracle.com>
> > > > 
> > > > Use the btree bulk loading functions to rebuild the reverse mapping
> > > > btrees and drop the open-coded implementation.
> > > > 
> > > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > > > ---
> > > >  libxfs/libxfs_api_defs.h |    1 
> > > >  repair/agbtree.c         |   70 ++++++++
> > > >  repair/agbtree.h         |    5 +
> > > >  repair/phase5.c          |  409 ++--------------------------------------------
> > > >  4 files changed, 96 insertions(+), 389 deletions(-)
> > > > 
> > > > 
> > > ...
> > > > diff --git a/repair/phase5.c b/repair/phase5.c
> > > > index e570349d..1c6448f4 100644
> > > > --- a/repair/phase5.c
> > > > +++ b/repair/phase5.c
> > > ...
> > > > @@ -1244,6 +879,8 @@ build_agf_agfl(
> > > >  	freelist = xfs_buf_to_agfl_bno(agfl_buf);
> > > >  	fill_agfl(btr_bno, freelist, &agfl_idx);
> > > >  	fill_agfl(btr_cnt, freelist, &agfl_idx);
> > > > +	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> > > > +		fill_agfl(btr_rmap, freelist, &agfl_idx);
> > > 
> > > Is this new behavior? Either way, I guess it makes sense since the
> > > rmapbt feeds from/to the agfl:
> > 
> > It's a defensive move to make sure we don't lose the blocks if we
> > overestimate the size of the rmapbt.  We never did in the past (and we
> > shouldn't now) but I figured I should throw that in as a defensive
> > measure so we don't leak the blocks if something goes wrong.
> > 
> > (Granted, I think in the past any overages would have been freed back
> > into the filesystem...)
> > 
> 
> I thought that was still the case since finish_rebuild() moves any
> unused blocks over to the lost_fsb slab, which is why I was asking about
> the agfl filling specifically..

Ah, right.  Ok.  I'll add a note to the commit message about how now we
feed unused rmapbt blocks back to the AGFL, similar to how we would in
regular operation.

--D

> Brian
> 
> > Thanks for the review.
> > 
> > --D
> > 
> > > Reviewed-by: Brian Foster <bfoster@redhat.com>
> > > 
> > > >  
> > > >  	/* Set the AGF counters for the AGFL. */
> > > >  	if (agfl_idx > 0) {
> > > > @@ -1343,7 +980,7 @@ phase5_func(
> > > >  	struct bt_rebuild	btr_cnt;
> > > >  	struct bt_rebuild	btr_ino;
> > > >  	struct bt_rebuild	btr_fino;
> > > > -	bt_status_t		rmap_btree_curs;
> > > > +	struct bt_rebuild	btr_rmap;
> > > >  	bt_status_t		refcnt_btree_curs;
> > > >  	int			extra_blocks = 0;
> > > >  	uint			num_freeblocks;
> > > > @@ -1378,11 +1015,7 @@ _("unable to rebuild AG %u.  Not enough free space in on-disk AG.\n"),
> > > >  	init_ino_cursors(&sc, agno, num_freeblocks, &sb_icount_ag[agno],
> > > >  			&sb_ifree_ag[agno], &btr_ino, &btr_fino);
> > > >  
> > > > -	/*
> > > > -	 * Set up the btree cursors for the on-disk rmap btrees, which includes
> > > > -	 * pre-allocating all required blocks.
> > > > -	 */
> > > > -	init_rmapbt_cursor(mp, agno, &rmap_btree_curs);
> > > > +	init_rmapbt_cursor(&sc, agno, num_freeblocks, &btr_rmap);
> > > >  
> > > >  	/*
> > > >  	 * Set up the btree cursors for the on-disk refcount btrees,
> > > > @@ -1448,10 +1081,8 @@ _("unable to rebuild AG %u.  Not enough free space in on-disk AG.\n"),
> > > >  	ASSERT(btr_bno.freeblks == btr_cnt.freeblks);
> > > >  
> > > >  	if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
> > > > -		build_rmap_tree(mp, agno, &rmap_btree_curs);
> > > > -		write_cursor(&rmap_btree_curs);
> > > > -		sb_fdblocks_ag[agno] += (rmap_btree_curs.num_tot_blocks -
> > > > -				rmap_btree_curs.num_free_blocks) - 1;
> > > > +		build_rmap_tree(&sc, agno, &btr_rmap);
> > > > +		sb_fdblocks_ag[agno] += btr_rmap.newbt.afake.af_blocks - 1;
> > > >  	}
> > > >  
> > > >  	if (xfs_sb_version_hasreflink(&mp->m_sb)) {
> > > > @@ -1462,7 +1093,7 @@ _("unable to rebuild AG %u.  Not enough free space in on-disk AG.\n"),
> > > >  	/*
> > > >  	 * set up agf and agfl
> > > >  	 */
> > > > -	build_agf_agfl(mp, agno, &btr_bno, &btr_cnt, &rmap_btree_curs,
> > > > +	build_agf_agfl(mp, agno, &btr_bno, &btr_cnt, &btr_rmap,
> > > >  			&refcnt_btree_curs, lost_fsb);
> > > >  
> > > >  	build_inode_btrees(&sc, agno, &btr_ino, &btr_fino);
> > > > @@ -1479,7 +1110,7 @@ _("unable to rebuild AG %u.  Not enough free space in on-disk AG.\n"),
> > > >  	if (xfs_sb_version_hasfinobt(&mp->m_sb))
> > > >  		finish_rebuild(mp, &btr_fino, lost_fsb);
> > > >  	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
> > > > -		finish_cursor(&rmap_btree_curs);
> > > > +		finish_rebuild(mp, &btr_rmap, lost_fsb);
> > > >  	if (xfs_sb_version_hasreflink(&mp->m_sb))
> > > >  		finish_cursor(&refcnt_btree_curs);
> > > >  
> > > > 
> > > 
> > 
>